1. Field of the Invention
The present invention relates to a packet transfer equipment and a server, and particularly relates to a packet transfer equipment that transfers the packet based on the information contained in the received packet and a server to resolve the transfer method for the packet based on the information contained in the packet.
2. Description of the Related Art
Packet transfer equipments that transfer the received packet based on the information contained in such packet include the following equipments in case of those currently used in the IP (Internet Protocol) network, for example:
(i) Layer 2 switch that determines the packet transfer method using the information contained in the MAC header (such as destination MAC address and VLAN-ID);
(ii) Layer 3 switch or a router that determines the packet transfer method using the information contained in the IP header (such as the destination IP address);
(iii) Layer 4 switch that decides the packet transfer method using the information contained in the IP header and the TCP/UDP header (such as the port No.); and
(iv) Layer 7 switch that determines the packet transfer method using the information (such as URL (Universal Resource Locator) and Cookie) contained in the application level header (such as the HTTP (HyperText Transport Protocol) header and the RTSP (Real Time Streaming Protocol) header).
These packet transfer equipments need the information about correspondence between the information contained in the received packet and the packet transfer method in order to determine the transfer method for the received packet. Conventional packet transfer equipments use three methods as follows to obtain such information:
(a) To use the information statically set inside of the packet transfer equipment by command line interface (CLI), NMS (Network Management Server) or the like;
(b) To use the information dynamically advertised to the packet transfer equipment using the information advertised from other node by the routing protocol or the like, and
(c) To make an inquiry to an external server.
The present invention improves the method (c) among these methods.
Conventional examples in which a packet transfer equipment inquires of an external server about the correspondence information between the information contained in the received packet and the transfer method for such packet include the “proxy arp” method by which the MAC address corresponding to a certain IP address is inquired of the router and a method by which the web proxy server inquires of the DNS (Domain Name System) server about the IP address of the corresponding server based on the FQDN (Fully Qualified Domain Name) of the URL contained in the HTTP request from the user.
According to the prior arts, the packet transfer method may be asked to an external server by the proxy arp method or by the inquiry of the DNS server from the web proxy server as described above. However, these methods only make a one-to-one conversion in which one piece of information in a particular field contained in the packet to another piece of information in a particular fixed field. Specifically, the proxy arp method converts the IP address to the MAC address and the web proxy server converts the FQDN to the IP address. They just serve for resolution of the limited one-to-one correspondence.
FIG. 23 is a matrix showing combinations between the types of information contained in the packet and the types of information related to the transfer method. In the columns classifying the types of information contained in the packet, the column “1 type (Fixed)” represents that one predetermined type of information is used as the key to find the transfer method regardless of the received packet. The column “1 type (determined for each packet)” represents that only one type of information is used as a key, but such type is determined for each received packet. The column “Several types (Fixed)” shows that several predetermined types of information are used as the keys regardless of the received packet. The column “Several types (Determined for each packet)” represents that there are several types of information used as the keys and that such several types are determined for each received packet. Further, in the lines classifying the types of information related to the transfer method, the line “1 type (Fixed)” represents that one predetermined type of information is used for resolution as the information related to the transfer method regardless of the received packet and the line “1 type (Determined for each packet)” shows that the information for resolution is one type, but that type is determined for each received packet. The line “Several types (Fixed)” shows that several predetermined types of information are used for resolution as the information related to the transfer method regardless of the received packet and the line “Several types (determined for each packet)” shows that there are several types of information for resolution and such several types are determined for each packet.
The proxy arp method and the conventional method using a web proxy server with inquiring of an external server about the packet transfer method correspond to the combination at A in the matrix of FIG. 23. Correspondence expressed by combinations at B to P other than A cannot be resolved using an external server according to the prior art. Specifically, the following correspondences cannot be resolved.
(1) Several arbitrary types of information contained in the received packet are used as the key to resolve one or more arbitrary type of information related to the packet transfer method (I to P). For example, using both the destination port number and the destination MAC address as the keys, the destination port number and the destination MAC address after conversion are resolved.
(2) One type of information contained in the received packet is used as the key, but the type of the key information is determined for each received packet (E to H). For example, the URL is rewritten using the URL as the key in a certain received packet and the MAC address is rewritten using the IP address as the key in another received packet.
(3) Using one fixed type of information contained in the received packet as the key, several arbitrary types of information related to the transfer method of that packet is resolved (C and D). For example, using the URL as the key, the URL after rewriting and the vlan tag to be added are resolved.
(4) Using one fixed type of information contained in the received packet as the key, one type of information related to the transfer method of that packet is resolved, but the type of the resolved information is decided for each received packet (B). For example, though the URL is used as the key for both cases, the URL after rewriting is resolved in a certain received packet and the MAC address is resolved in another received packet.
(5) Arbitrary combination of (1) to (4) above. For example, when there are two types of packets (Packet A and Packet B), the destination port No. and the destination MAC address are rewritten before transfer in case of packet A, but the URL is rewritten and the vlan tag is added before transfer in case of packet B.
To resolve the correspondence as in (1) to (5) described above, there is no other method than to statically set a resolution inside of the packet transfer equipment using CLI or NMS instead of an external server according to the prior art. By this method, however, it is necessary to set the packet transfer method for each packet transfer equipment and the packet transfer equipments cannot be managed collectively.
In addition, even if the transfer methods for correspondences (1) to (5) as described above are resolved by inquiry of an external server, it is necessary to provide a server for each type of information processing method. It is necessary to have a server to resolve the rewriting method of the destination port number, a server to resolve the rewriting method of the destination MAC address, a server to resolve the URL rewriting method, a server to resolve the method for vlan tag addition and so on. It is substantially impossible to actually have so many servers. It is further difficult to set a different transfer method for each packet.